Sea Level Change Flashcards
What is Eustatic Sea Level change?
The sea level changes due to an alteration in volume of water or change in ocean basin shape, hence amount of water that the sea can hold.
What effect does Eustatic sea level change have?
Global effect
When does Eustatic change take place?
During and after an ice age.
What happens at the beginning of an Ice Age?
Temp falls, water is frozen and stored in glaciers, suspending hydrological cycle. Sea level falls.
What happens at the end of an Ice Age?
Temp rises, water stored in glaciers re-enters cycle and the sea will replenish. Sea level rises.
Why does the ocean basin shape change?
Change due to tectonic movement.
What happens if the ocean basin becomes larger?
Volume of oceans increase, sea level falls.
What happens if the ocean basin becomes smaller?
Volume of oceans decrease, sea level rises.
What is Isostatic Sea Level change?
Result of an increase or decrease in height of land. If land height increases, sea level decreases. If land height decreases, sea level rises.
What effect does Isostatic sea level change have?
Local/regional effect.
Isostatic change DURING an ice age
Ice builds up on land, increasing weight of land and therefore it sinks. Sea level slightly rises.
Known as COMPRESSION
Isostatic change at the END of an ice age
Land rises as ice melts, sea level falls.
Known as DECOMPRESSION (or ISOSTATIC REBOUND)
How is Isostatic change caused by tectonic uplift/depression?
It takes place at plate boundaries an therefore only occurs in certain areas of the world.
When do emergent landforms appear?
Towards the end of an ice age as isostatic rebound takes place faster than eustatic rise in sea level.
(Lands height rises faster than the seas)
Where do emergent landforms occur?
They develop at the previous sea level and emerge above sea as land rises.
Example of an emergent landform
Raised Beaches are wave-cut platforms and beaches above current sea level. Relic cliffs are also found behind raised beaches with features such as notches, arches and stacks.
Are emergent features eroded?
They no longer experience erosion but are still weathered; biologically, chemically and freeze-thaw.
How are submergent landforms formed?
They form when eustatic rise in sea level takes place faster than isostatic rebound after an ice age.
Water flood land and fills up the landforms.
Submergent landform example: Ria
River valley flooded by eustatic rise. Like a typical valley but filled with larger amount of water and their floodplain also gets flooded.
Submergent landform example: Fjord
They are flooded glacial valleys. Steeper and deeper than a Ria and are relatively narrow for their size. U-shaped profile and found particularly in icy parts of the world. Shallow mouth where glacier deposited its load.
Submergent landform example: Dalmation coastline
Form where valleys lie parallel to each other. When flooded tops f valleys remain above surface and appear as islands running parallel to coastline.
Example of a Fjord
Sogne Fjord, Norway
Example of a Dalmation Coastline
Dalmation coast, Croatia
Why are sea levels still rising?
- Still coming out of last ice age so isostatic rebound still taking place.
- Planets getting hotter, causing more ice to melt.
